The catalyzed reaction of methanol and ammonia to produce the mono-, di-, and trimethylamines is well known in the art. Presently, the methylamines are produced commercially by a continuous process for methanol and ammonia using an amorphous silica-alumina catalyst. This continuous process yields an equilibrium controlled distribution of the methylamines.
U.S. Pat. No. 3,384,667 discloses a method for producing monosubstituted and disubstituted amines in preference to trisubstituted amines by reacting ammonia with an alcohol in the presence of a crystalline metal aluminosilicate catalyst having pores of a diameter that pass the monosubstituted and disubstituted amine products but are too small to pass the trisubstituted amine product. Hydrogen exchanged crystalline aluminosilicates are defined as crystalline metal aluminosilicates in the patent.
U.S. Pat. No. 4,082,805 discloses a process for the production of aliphatic amines by reaction of a C.sub.1 -C.sub.5 alcohol or ether with ammonia in the presence of a catalyst comprising a crystalline aluminosilicate having the structure of ZSM-5, ZSM-11 or ZSM-21, at 300.degree. to 500.degree. C. and at one atmosphere to 1000 psig pressure, the feed rate of alcohol or ether and ammonia being within the ratio of 1:1 to 5:1 g/hr.
U.S. Pat. No. 4,191,709 discloses a process for the manufacture of amines by reacting an alcohol with ammonia in the presence of the hydrogen form of zeolite FU-1 or zeolite FU-1 in which some or all of the protons have been replaced by bivalent or trivalent cations. The related U.S. Pat. No. 4,205,012 is similar except that the catalyst comprises zeolite FU-1 in which some or all of the protons have been replaced by monovalent cations, for example, sodium.
U.S. Pat. No. 4,229,374 discloses a process for producing tertiary amines by reacting alcohols with ammonia, primary amines or secondary amines in the presence of a specific catalyst. The catalyst comprises a mixture of copper, tin and an alkali metal supported on a suitable carrier, such as artificial and natural zeolites.
U.S. Pat. No. 4,254,061 discloses a process for producing monomethylamine by reacting methanol and ammonia, in such amounts so as to provide a C/N ratio, from the methanol and ammonia reactants, of 0.5-1.5, over a catalyst which is (a) mordenite wherein the primary cation is Li, Na, HNa having at least 2% Na by weight, K, Ca, Sr, Ba, Ce, Zn or Cr; (b) ferrierite wherein the primary metal cation is Li, Na, K, Ca, Sr, Ba, Ce or Fe; (c) erionite ore; (d) calcium erionite; or (e) clinoptilolite ore.
With a silica-alumina catalyst, reactor inlet temperatures of about 600.degree. to 650.degree. F. (316.degree. to 343.degree. C.) are typically used. The maximum temperature in the reactor must be maintained below about 800.degree. F. (427.degree. C.) to avoid thermal and wall reactions that lead to hydrocarbon by-products, catalyst coking and poor yields. The amination reactions are exothermic, so that in an adiabatic plugged flow reactor the temperature rises by 150.degree.-450.degree. F. (66.degree.-232.degree. C.) depending on the ammonia:methanol feed ratio. With an inlet temperature of about 600.degree. to 650.degree. F. (316.degree. to 343.degree. C.) and such maximum temperature restriction, the feed ratio of ammonia:methanol is limited to about 2.2:1 or higher in order to avoid a temperature rise in the reactor in excess of 800.degree. F. (427.degree. C.) with the attendant high temperature problems. Thus, improving methanol conversion rates would offer advantages such as lower reactor inlet temperatures permitting lower ammonia:methanol feed ratios and less excess ammonia to handle.